#include <GL/freeglut_std.h>
#include <GL/gl.h>
#include <GL/glut.h>
// Called to draw scene
void RenderScene(void) {
  // Clear the window with current clearing color
  glClear(GL_COLOR_BUFFER_BIT);
  // Set current drawing color to red :R G B
  glColor3f(1.0f, 0.0f, 0.0f);
  // Draw a filled rectangle with current color
  glRectd(100.0f, 150.0f, 150.0f, 100.0f);
  // Flush drawing commands
  glFlush();
}

// Setup the rendering state
void SetupRC(void) {
  // Set clear color to blue
  glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
}
// Called by GLUT library when the window has cahnge size
void ChangeSize(GLsizei w, GLsizei h) {
  // Prevent a divide by zero
  if (h == 0)
    h = 1;
  // Set Viewport to window dimensions
  glViewport(0, 0, w, h);

  // Reset coordinate system
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  // Establish clipping volume (len, right, booom, top,near, far)
if (w <= h)
glOrtho (0.0f, 250.0f, 0.0f, 250.0f*h/w, 1.0, -1.0);
else glOrtho(0.0f, 250.0f * w / h, 0.0f, 250.0f, 1.0, -1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

// Main program entry point
int  main(int argc, char **argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(400, 350);
  glutInitWindowPosition( 10, 10);
  glutCreateWindow("GLUT: GLRect");
  glutDisplayFunc(RenderScene);
  glutReshapeFunc(ChangeSize);
  SetupRC();
  glutMainLoop();
}